Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8603—Removing sulfur compounds
  • B01D53/8612—Hydrogen sulfide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B17/00—Sulfur; Compounds thereof
  • C01B17/02—Preparation of sulfur; Purification
  • C01B17/04—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides
  • C01B17/0404—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process
  • C01B17/046—Preparation of sulfur; Purification from gaseous sulfur compounds including gaseous sulfides by processes comprising a dry catalytic conversion of hydrogen sulfide-containing gases, e.g. the Claus process without intermediate formation of sulfur dioxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
  • C01B2203/1205—Composition of the feed
  • C01B2203/1211—Organic compounds or organic mixtures used in the process for making hydrogen or synthesis gas
  • C01B2203/1235—Hydrocarbons
  • C01B2203/1241—Natural gas or methane
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
  • C01B2203/1258—Pre-treatment of the feed
  • C01B2203/1264—Catalytic pre-treatment of the feed
  • C01B2203/127—Catalytic desulfurisation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/12—Feeding the process for making hydrogen or synthesis gas
  • C01B2203/1276—Mixing of different feed components
  • C01B2203/1282—Mixing of different feed components using static mixers

Definitions

• H S for plants producing more than 100,000 tons of sulfur per year.
• the Claus process is not suitable for use in cleaning up hydrogen or light hydrocarbon gases (such as natural gas) that contain H S, however. Not only is the hydrocarbon content lost in the initial thermal combustion step of the Claus process, but carbon, carbonyl sulfide and carbon disulfide which are produced cause catalyst fouling and dark sulfur. Moreover, carbonyl sulfide is difficult to convert to elemental sulfur.
• various changes to the Claus process have been suggested, many of which are directed primarily toward improving or replacing the thermal reactor. See, for example, U.S. Patent Nos. 4279882, 4988494, 5597546 and 5653953.
• reaction (4) is not a thermodynainically reversible reaction
• direct oxidation techniques offer potentially higher levels of conversion than is typically obtainable with thermal and catalytic oxidation of H 2 S.
• Most direct oxidation methods are applicable to sour gas streams containing relatively small amounts of H 2 S and large amounts of hydrocarbons, but are not particularly well suited for handling the more concentrated acid gas streams from refineries. For this reason direct oxidation methods have been generally limited to use as tail gas treatments only, and have not found general industrial applicability for first stage sulfur removal systems from gases containing large quantities of H 2 S.
• the acid gas stream for the modified Claus process should contain less than 2 mole % of light hydrocarbons and from 15 to essentially 100% H 2 S.
• U.S. Pat. Nos. 5,451,557 and 5,573,991 disclose other processes for forming a metal carbide catalyst such as tungsten carbide or another Group VIB transition metal carbide.
• U.S. Pat. No. 4,331,544 (Takaya et al.) describes a catalyst for catalyzing the synthesis of methane from CO and H 2 . That catalyst comprises a nickel-molybdenum alloy and a molybdenum carbide supported on a porous carrier. Still other metal carbide catalysts are disclosed in U.S. Pat. Nos. 4,219,445 (Finch), 1,930,716 (Jaeger), and 4,271,041 (Boudart et al.).
• the present process also provides an improvement over other catalytic direct oxidation methods for converting H 2 S directly to sulfur by eliminating the need to limit the operating temperature to below the dew point of sulfur, or below 500°C, and avoids the need for a large stoicl iometric excess amount of O 2 .
• the new process also overcomes a usual disadvantage of existing direct oxidation methods by efficiently desulfurizing gases containing a higher concentration of H S than is possible with the existing methods. Under preferred optimal conditions, the level of H 2 S conversion obtained in a single pass process is high enough that no additional, or tail gas treatment of the exiting gas is necessary.
• Ensuring SCPOX reaction promoting conditions may include adjusting the relative amounts of H 2 S, O 2 and other oxidizable components (e.g., hydrocarbons) in the feed gas mixture. For example, preferably no more than a stoichiometric amount of O 2 , relative to the carbon content of the feed mixture, sufficient to support the CPOX reaction is provided, in order to deter oxidation of other components in the feed.
• SCPOX reaction promoting conditions may also include adjusting the amount of preheating of the reactant gas mixture and/or external heat applied to the catalyst, adjusting the operating pressure of the reactor, which is preferably maintained above atmospheric pressure, more preferably in excess of two atmospheres pressure.
• the process comprises, in a millisecond contact time reactor, passing the H 2 S-containing gas stream, mixed with O 2; in a molar ratio of about 2:1 H 2 S:O 2 , over the catalyst device such that the above-described partial oxidation reaction occurs.
• the temperature of the mixing zone and the reaction zone are maintained above the dewpoint of sulfur, to avoid deposition of sulfur inside the reactor.
• the process also includes maintaining the temperature of the catalyst device sufficiently high to substantially prevent sulfur poisoning of the catalyst device.
• the catalyst temperature is maintained at or above about 700°C, preferably below 1,500°C, and more preferably in the range of 850°C-1,300°C. especially when a metal is employed that is susceptible to sulfur poisoning.
• the contact time between the catalytic surfaces of the catalyst device and the gas stream is maintained at is no more than about 200 milliseconds, preferably under 50 milliseconds, and more preferably less than 20 milliseconds. Less than 10 millisecond contact time is highly preferred.
• a product stream comprising liquid elemental sulfur is recovered.
• a desired gaseous product is preferably also recovered.
• the H 2 S containing gas also contains a light (i.e., -Cs) hydrocarbon, such as methane, and the desulfurized hydrocarbon gas is recovered. There may be instances where hydrocarbons greater than C 5 are also present in small quantities, and they are also recoverable essentially unharmed by the process.
• the H 2 S-containing stream also contains H 2 , and the process recovers a substantially sulfur-free H 2 product stream which is suitable for feeding back into an H -consuming process, such as a hydrotreater.
• Fig. 1 is a schematic flow diagram for one embodiment of a system employing the H 2 S recovery process of the present invention.
• Fig. 2 is an enlarged cross-sectional view of the millisecond contact time reactor shown in Fig. 1.
• Fig. 3 is a diagram of an embodiment of a natural gas purification system for carrying a process in accordance with the present invention.
• Rh on a Ln-modified Refractory Support Another type of catalyst that is active for catalyzing the direct partial oxidation of H 2 S to elemental sulfur comprises about 0.005 to 25 wt% Rh, preferably 0.05 to 25 wt%> Rh, and about 0.005 to 25 wt%> of a lanthanide element (i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), preferably samarium, ytterbium or praseodymium, in the fonn of the metal and/or metal oxide coating a refractory monolith or a plurality of distinct or discrete structures or particulates.
• a lanthanide element i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu
• a lanthanide element i.
• At least a majority (i.e., >50%>) of the particles or distinct structures have a maximum characteristic length (i.e., longest dimension) of less than ten millimeters, preferably less than five millimeters.
• the term "monolith” refers to any singular piece of material of continuous manufacture such as solid pieces of metal or metal oxide or foam materials or honeycomb structures. Two or more such catalyst monoliths may be stacked in the catalyst zone of the reactor if desired.
• the supports preferably comprise a refractory material such as zirconia, alumina, cordierite, titania, mullite, zirconia-stabilized alumina, MgO stabilized zirconia, MgO stabilized alumina, niobia or a mixture of any of those materials, or another suitable refractory material.
• Alumina is preferably in the form of alpha- alumina, however the other forms of alumina have also demonstrated satisfactory performance.
• Catalytic device 47 is preferably in the form of a fixed layer or layers of wire gauze, a porous monolith, or a packed bed of divided material. Preferred operating conditions for the reactor are described below.
• the hydrogen and H S gas mixture is separated from the desulfurized oil in hot high pressure (HHP) separator 22, and the gas mixture is cooled in heat recovery exchanger 24 (in conjunction with heating of recycled and/or makeup H 2 in route to the HDS reactor).
• the H /H 2 S gas is then cooled in air cooler 26 and water cooler 28 before entering cold high pressure (CHP) separator 30.
• Desulfurized light oil and sour H O are removed from CHP separator 30 and the mixed H 2 and H 2 S stream is routed to the short contact time reactor 40.
• oxygen enters reactor 40 via oxygen inlet conduit 41 and is mixed with the H 2 /H 2 S stream by mixer 50 within mixing zone 48.
• the H 2 S-containing stream may contain only a trace amount of H 2 S, a small amount (e.g., 0.5 -1 vol.%o), more than 3 - 25 vol.%» H S, up to 40 vol.%) (as in some natural gas reserves, for example), or can even consist of a 100%> H 2 S stream.
• the temperature of the reactant gas mixture is at least about 200°C to facilitate initiation of the reaction.
• the mixing of the gases must be very thorough to prevent combustion reactions from taking place or predominating in the reaction zone to form SO 2 .
• Ten milliseconds or less contact time is highly preferred. This very brief gas residence time on the catalyst is important to minimize or eliminate the formation of SO 2 that would restrict the recovery of sulfur by establishing the Claus equilibrium of equation (3).
• the flow of the reactant and product gases is maintained at a rate sufficient to provide a GHSV of at least about 100,000 hr "1 .
• the process is operated at atmospheric or superatmospheric pressures, the latter being preferred.
• the pressures may be from about 100 kPa to about 12,500 kPa, preferably from about 130 kPa to about 10,000 kPa.
• An advantage of employing the above-described short contact time partial oxidation process instead of a conventional partial oxidation method is that greater concentrations of H 2 S in the reactant stream can be processed by the new method than has generally been possible with known processes.
• the catalytic partial oxidation of hydrogen sulfide has been shown by the present inventor in co-assigned applications 09/625,710 and 09/624,715 to be useful for improving synthesis gas production and for concurrently producing hydrogen gas. The disclosures of those applications are incorporated herein by reference.
• Apparatus that is well known in the art for injecting gas into short contact time reactors at high flow rates is employed to feed the reactant gases at atmospheric or superatmospheric pressure.
• Oxygen entering reactor 140 via inlet 141 is mixed with the H 2 S/natural gas stream in mixing zone 148.
• Air, or an oxygen enriched air stream could also be used; however, substantially pure oxygen is preferred as it prevents the inclusion of inert gases such as nitrogen and argon in the system.
• a mixer (such as static mixer 50 depicted in Fig. 2) evenly distributes the O 2 across the entire cross section of reactant gas conduit 144. Thorough mixing deters the occurrence of unwanted side reactions and temperature excursions in the reaction zone 145, as discussed in Example 1.

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• 2001
  • 2001-12-18 CA CA002430600A patent/CA2430600C/en not_active Expired - Fee Related
  • 2001-12-18 WO PCT/US2001/048795 patent/WO2002057002A1/en not_active Application Discontinuation
  • 2001-12-18 AT AT01993301T patent/ATE416023T1/de not_active IP Right Cessation
  • 2001-12-18 AU AU2002245146A patent/AU2002245146B2/en not_active Ceased
  • 2001-12-18 DE DE60136854T patent/DE60136854D1/de not_active Expired - Lifetime
  • 2001-12-18 EP EP01993301A patent/EP1355720B1/de not_active Expired - Lifetime

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